1. Field
Embodiments of the present invention relate to a rotary valve including a rotor which is rotated to open and close a flow passage.
2. Description of Related Art
In an engine (internal combustion engine) of a vehicle such as an automobile, for the purpose of enhancing the warm-up performance of the engine, enhancing the fuel efficiency by operating the engine at an optimal temperature, and the like, it is considered that a bypass passage through which cooling water bypasses a radiator and is returned to the engine as it is provided separately from a main passage through which the cooling water is circulated between the engine and the radiator, a cooling water control valve is provided in the main passage, and by controlling the opening degree of the cooling water control valve according to the temperature of the cooling water and the other values, the amount of the cooling water which flows through the main passage and is cooled by the radiator is controlled. Note that the cooling water is circulated by a pump driven by the engine, and during an operation of the engine, the cooling water is mainly circulated through the main passage in a case where the cooling water control valve is opened, and is circulated through the bypass passage in a case where the cooling water control valve is closed.
For example, during the start-up of the engine at a low cooling water temperature, the main passage is blocked to allow the cooling water to return to the engine as it is from the bypass passage without passing through the radiator, thereby accelerating the warm-up of the engine. In addition, for example, in order to control the temperature of the cooling water to optimize the combustion of a fuel in the engine even after the warm-up, opening and closing (the opening degree) of the cooling water control valve is adjusted.
In the cooling water control valve, the use of a rotary valve or the like is considered (for example, see Patent Literature 1).
In addition, a rotary valve has been proposed which is not the above-described valve for cooling water but is a valve used in an automobile (for example, see Patent Literature 2 and Patent Literature 3).
In a rotor of such a rotary valve, a flow passage for connecting an end surface to an outer circumferential surface of the rotor is provided therein, the rotor is rotated to move a position of the opening on the outer circumferential surface side of the rotor in the flow passage in a circumferential direction, and thus the valve is opened and closed.
Basically, an inside diameter of the flow passage provided in the rotor is substantially equal to a diameter of a connection part with an external flow passage, and, for example, is smaller than two thirds of an outer diameter of the rotor. That is, the passage having a diameter substantially equal to that of an inflow port and an outflow port of the valve is provided in the rotor, and the diameter of the rotor is quite large relative to the diameter of the flow passage.